Fast Five Quiz: Aromatic L-amino Acid Decarboxylase Deficiency (AADCD) Clinical Characteristics

Stephen L. Nelson, Jr, MD, PhD


August 13, 2021

Patients with a mild phenotype may not have movement disorders and might present instead primarily with autonomic symptoms like diarrhea, episodic hypoglycemia, nasal congestion, profuse nasal and oropharyngeal secretions, and excessive sweating. Ptosis and temperature instability may also be presented but are less common.

More than 50 different DDC gene disease–causing variants have been described in AADCD, but clear genotype/phenotype correlations have not been defined. However, almost all patients with the founder splice variant IVS6 + 4A > T had a severe phenotype.

Sex is not associated with phenotype in AADCD; the severe phenotype is seen in both females and males (72% of female patients and 77% of male patients).

Plasma AADC enzyme activity does not correlate with clinical phenotype. CSF values of biogenic amines may vary regardless of disease severity and may fall below the detection limit of the assay in mild and severe cases alike.

Learn more about AADCD phenotypes.


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